Try the following. Most likely this will fix your issue. If this does, TrueNAS has a fix that is in it's next update.
Login to TrueNAS interface.
Left side select "system".
Then after screen refreshes select "shell" from the list.
Paste in the following command. *Can't use normal short cuts* Will need to use Shift + Insert Key for pasting.
sudo python /usr/lib/python3/dist-packages/middlewared/scripts/vendor_service.py
If that works within about 1 min you should be able to go to deck.hexos.com and see your server or claim it.
You might need to run this after reboots.
Let us know if this works.
Thank you,